This invention relates to the feeding of sheets seriatim from a stack of sheets on a support surface. Such support surfaces are provided with edge margin guides for engaging the sides of the stack in order to keep the sheets in proper registration. When a support surface is required to accommodate sheets of different widths, the distance between the edge margin guides must be adjustable.
In some arrangements, the edge margin guides are mounted in different sets of holes or slots in the support surface, or blocks of different widths are provided for building out a fixed edge margin guide to the correct position for the edge of the stack. In both these arrangements, the adjustment of the effective surface of the edge margin guide is in descrete steps. British patent specification No. 1284832 discloses edge margin guides which are located by spring loaded balls in discrete steps engaging spaced recesses.
Continuous adjustment of the edge margin guides has also been proposed, but with such continuous adjustment it becomes more difficult to position the edge margin guides accurately symmetrically about the center line of the support surface, and connecting linkages had been proposed for ensuring that any movement of one edge margin guide is accompanied by movement of the other edge margin guide in the opposite direction by the same distance. The alignment of the center line of the sheets in the stack with the center line of the feed path through the machine is required so that the sheets should travel through the system without skewing.
An example of a connecting linkage for a pair of edge margin guides movably mounted on a support surface is disclosed in British patent specification No. 747,396. In the specification, two edge margin guides are supported by pins on a plate below the paper tray, the pins moving in a separate slot for each guide. The guides are linked by means of chains and sprockets so that movement of one edge guide is accompanied by an equal and opposite movement of the other guide, that is the edge guides are always symmetrical about the centre line of the apparatus. This linkage is expensive to manufacture and to tool-up, and it is possible that the movement of the edge guides may become unsynchronised due to wear or bending of the linkage.